in Irish music, "harp tune of a sportive and animated character" [OED], 1790, of unknown origin, evidently not a native Irish word; some suggest ultimate derivation from Latin plangere "to strike, beat" (see plague (n.)). See also [Katrin Thier, "Of Picts and Penguins -- Celtic Languages in the New Edition of the OED," in "The Celtic Languages in Contact," 2007.